. >> i never thought i would ever live to see children and babies slaughtered in america. >> reporter: he's now open to the possibility of banning large magazines. after getting a call from president obama today, manchin put out a statement saying "we must work together to keep our precious children safe." in congress, three democrats with long histories as gun control advocates are taking the lead with proposals to ban both military-style assault weapons and high-capacity magazines show me how this works. how quickly can you change a magazine? >> it's out; it's in. >> reporter: but at a northern virginia gun store today, this instructor said banning large magazines like this one with 30 rounds is futile. >> he could have had ten-round magazines and changed those just as quickly before police got there and it wouldn't have made one difference in the carnage that he caused. >> reporter: he wanted to show us the 60-round magazine, scott, but he couldn't because the store has sold out its entire inventory of about 2,000 large magazines in just the past four days. he said gun owners are s